Coldwater Rumble Course Guide

It depends on which distance you pick. The Coldwater Rumble is a desert trail race at Estrella Mountain Regional Park near Phoenix, and the 40K and 60K are very doable if you show up trained, but the 100K and especially the 100 mile are serious ultras. The course is not mountainous and the climbing rolls instead of going alpine, and the elevation is low desert so altitude is not a thing here. What actually wears you down is the effort piling up over a multi-loop course, the sandy and rocky footing, and a January day that is usually mild but can turn warm in the sun or cold at night. The 100 mile carries roughly 10,000 feet of total gain and a 32 hour cutoff. It earns its buckle.

The 100 mile course carries roughly 10,000 feet of cumulative gain, and it is spread across repeated loops through the foothills of the Sierra Estrella range, not stacked into one or two big climbs. The shorter distances get proportionally less since each one runs a chunk of the same loop network. There is no sustained mountain ascent and no altitude. The vert comes at you in short rolling punches, over and over. That changes how you train, so think runnable hills and legs that hold up for hours, not one giant alpine grind. Always confirm the exact per-distance gain for your edition on the official race page.

Fuel like it is a long, dry, mostly mild day out, because that is what it is. Most runners aim for 60 to 90 grams of carbohydrate per hour, and you can lean toward the high end on the 100K and 100 mile once your gut is trained for it. For sodium, bias it to your own sweat rate, often in the 500 to 800 mg per liter of fluid range, because the dry desert air pulls sweat off you that you may not even feel. The loops are a gift here. You come back past the start area aid hub every lap, so you can stage drop bags and reset your nutrition each time around. Practice your hourly carb and fluid numbers in training first. Our free ultra fueling calculator builds a personalized carb, sodium, and fluid plan per hour for your distance and the conditions you expect.

The 100 mile has an overall cutoff around 32 hours, with both a standard finisher buckle and a sub-24 hour buckle up for grabs, and the shorter distances have their own tighter limits scaled to the distance. There are also intermediate cutoffs tied to the loops, so you cannot bank an easy first lap and then crawl the rest. The exact intermediate and per-distance times can change year to year, so build your pacing plan backward from the official cutoff chart for your edition, and leave yourself a buffer, so the repeated laps and the night out on the 100 do not put you behind the clock.

It is classic Sonoran desert trail: crushed granite singletrack, rocks and boulders, old jeep roads and dry wash beds, plus sandy sections. There is one notably sandy stretch (the Corgett Wash area) where most people run gaiters to keep grit out of their shoes. None of it is alpine or super technical in the mountain sense. But the sand and loose granite quietly beat up your feet and ankles over a long day, and sand slows your pace and burns extra energy on top of that. Train your feet and lower legs for it, and sort out your shoe and gaiter setup before race day.

Usually no on both counts. It runs in mid-January in the low desert near Phoenix, and at roughly 950 to 1,300 feet altitude is basically a non-factor. Daytime highs are typically around the 60s and overnight lows around the 40s, which is about as nice as ultra weather gets in winter. That said, the desert sun can still feel warm midday out on exposed trail, and a clear desert night gets genuinely cold, so dress in layers you can pull off and put back on, and do not get caught underdressed for the night on the 100 mile or the cold pre-dawn start.

Match your training to the distance and to this rolling, runnable desert terrain. For the 100 mile, build a big durable aerobic base and practice running on tired legs through the night. For the 100K, build the endurance to keep moving efficiently for 12 hours or more. For the 40K and 60K, just get in solid long runs and time on rolling trail. No matter the distance, get comfortable on loose and sandy footing, rehearse your fueling, and practice power hiking the short steep pitches. Summit Line can build a plan dialed to your current fitness and this exact course profile.